There are a large number of signaling apparatuses at airports, such as lighting devices, which may be located in particular on or in the vicinity of taxiways, ramps, taxiways or runways, or else, for example, on buildings such as hangers, on the tower or on other facilities. Signaling apparatuses may also include, for example, radar devices or radio beacons.
Airport lighting systems are currently known which are used essentially for monitoring the lamp function of the individual airport lights and in this case replace simple open-loop and closed-loop control signals. The power range of known systems such as these is restricted considerably, primarily as a result of serious interference factors. For example, the electrical characteristics of the cables that are used for communication change as a result of the varying moisture in the ground and as a result of aging phenomena, as well as a result of the requirements for airfield operation becoming particularly stringent. Particularly in the case of airport operation, interference occurs to an unusual extent, severity and with an unusual irregularity as a result of other systems. Interference influences are caused, for example, by on-board electrical power supply systems, on-board radars, stationary radars, radio links or other mobile radio systems, network command receivers, power and control cables located parallel to one another, reinforcing iron in ground fittings, fuel lines installed in the surfaces, and as a result of static charges which are caused by flying operations.
WO 95/24820 describes a communication system of the type mentioned initially for a series circuit, with communication taking place only in narrowly delineated time periods, with the delineation of the time periods, with the time periods being delineated as a function of the frequency of the circuit, in order to avoid interference influences from harmonics. The synchronization between the time intervals for communication and the frequency of the circuit is in this case relatively complex and extends.